1975-02-22 SW OK Elevated Supercell Tornadoes

[Brett Roberts]

I recently came across this shockingly bizarre case online: several tornadoes, some significant, ravaged portions of SW OK during the early morning of 22 Feb 1975. Altus, OK, received F2 damage from a tornado that struck just after midnight. The catch? Surface temperatures were in the 30s and 40s with strong north winds, as the area was well north of a strong front that stretched across N TX. In fact, winter precipitation occurred shortly after the event.

Jon Finch's site (www.bangladeshtornadoes.org) provides several relevant charts:

Tornado tracks

Surface map (22/04z)
H5 map (22/00z)

Needless to say, the parent thunderstorms were rooted above a stable boundary layer, and in this case a steep inversion. The NCEP/NCAR Reanalysis tool on Plymouth State's site depicts 850 mb temperatures of 8-12 C over SW OK, and 700 mb southerlies of 30-40 kt suggestive of overrunning.

Though not spatially or temporally all that close to the tornado reports, the 22/00z OUN sounding might be of interest. Just eyeballing a parcel originating from the top of the inversion (~875 mb), MUCAPE appears to be modest but not negligible. Deep-layer shear is very impressive, and in fact the upper-air charts all around look like something we'd be salivating over in April or May.

It's a shame there were no soundings taken very close to the reports in space and time, as I'd be awfully interested to see the strength and depth of the inversion. If anyone else has more info relating to this event, please feel free to post, since I wasn't able to find a whole lot.

If I worked at SPC, this event would probably have me biting my nails every time a blue norther rolled into TX/OK with strong elevated convection behind the surface front...

 

[Steven Williams]

I would say theres a mix up of the information/dates there Brett. The report doesn't look believable.

 

[GPhillips]

If Jon Finch and the Norman WFO both have a listing of tornadoes for that place and time, I'd believe it.

http://www.srh.noaa.gov/oun/?n=tornadodata-ok-februarytornadoes

The general case of cold weather tornadoes was discussed in this thread from a few years ago:

http://www.stormtrack.org/forum/sho...al-question-concerning-cold-weather-tornadoes

 

[Steven Williams]

The SE surface wind/moist unstable airmass would have been over southern Oklahoma at tornado time and the boundary has shifted south into Texas for the 04Z analysis.

 

[Brett Roberts]

The SE surface wind/moist unstable airmass would have been over southern Oklahoma at tornado time and the boundary has shifted south into Texas for the 04Z analysis.

Actually, the tornado reports occurred between 06z and 09z. This case is documented and noted for featuring an elevated-storm environment in a few other places (for example, in this Q&A from USA Today, where Harold Brooks of NSSL mentions it near the bottom of the page: http://www.usatoday.com/weather/wtwistqa.htm).

 

[mikedeason]

IIRC, Gary England has a few paragraphs about this event in his book, "Weathering the Storm."

 

[Jeff Duda]

Jon Finch's site (www.bangladeshtornadoes.com) provides several relevant charts:

I get a "site not found" error when clicking that link and going to that site. Are you sure it's not something else?

 

[Skip Talbot]

That 58/55 surface observation down in south central OK is not too far from where the tornado tracks occurred. Perhaps a strong overnight LLJ resulted in some dramatic warm air advection between the 4z chart and 6z-9z reports? Looking at that OUN sounding, that stable surface layer is really shallow. Perhaps updrafts were in reality occurring right on or just north of the warm front and with enough forcing to overcome that stable surface layer?

 

[Brett Roberts]

I get a "site not found" error when clicking that link and going to that site. Are you sure it's not something else?

Gah... that's what I get for not just copy-and-pasting the URL. Fixed now.

That 58/55 surface observation down in south central OK is not too far from where the tornado tracks occurred. Perhaps a strong overnight LLJ resulted in some dramatic warm air advection between the 4z chart and 6z-9z reports? Looking at that OUN sounding, that stable surface layer is really shallow. Perhaps updrafts were in reality occurring right on or just north of the warm front and with enough forcing to overcome that stable surface layer?

I was finally able to locate the article that originally piqued my interest in this case last week when I stumbled across it. From the March/April 2005 issue of WeatherWise:

Five tornadoes, all F1 or F2 on the
Fujita scale, touched down in the southwest
quadrant of Oklahoma between
12:30 and 3:00 a.m. on February 22,
1975. We shall concentrate on the F2
tornado in Altus, Oklahoma, which
struck at 12:35 a.m. At midnight in Altus,
the temperature was 41°F, dewpoint
26°. At the same time, 50 miles west–
southwest in Childress, Texas, the temperature
was 35°F, dewpoint 29°. Sleet
was falling, accompanied by lightning
and thunder. The sleet changed to snow
in Childress at 12:28 a.m., a few minutes
before the tornado hit Altus. Sleet
began in Altus just two and a half hours
after the tornado and changed to snow
within another hour.

In the article, Mike Foster (MIC at NWS OUN), Chuck Doswell, and Don Burgess are listed as people who were interviewed about the event. The data described in the quote above came from Burgess.

Based on this description, it seems clear that the boundary was a cold front pushing south with time that night. The article states the front was "175 miles southeast of Altus at the time of the tornado," though there are unfortunately no accompanying figures to verify this. Does anyone know where/if surface obs are available online going back to the 1970s?

 

[GPhillips]

Below is a link to the surface map from gempak for midnight CST.

http://www.flickr.com/photos/78383954@N05/7184200896/in/photostream/lightbox/

 

[DNewman]

Id be interested in more research about this event and re create a realistic to scenario with this.

Sent from my SAMSUNG-SM-G750A using Tapatalk

 

[calvinkaskey]

The 6 February Oklahoma tornadoes that day were all 100 yds wide or less and all may have lasted 6 minutes or less if they were traveling => 60mph.